1. Field of the Invention
The present invention is directed to methods of preparing dried blood products using spray-drying as an alternative to conventional lyophilization (freeze-drying), and products made by the method. Using the method of the invention, increased recovery rates of dried product are possible. The final product displays at least three-fold concentration over native plasma, as well as increased reconstitution rates when mixed with liquids.
2. Brief Description of the Related Art
Spray-drying is a technology in which a solution is atomized in a stream of flowing gas for rapid solvent vaporization (e.g., dehydration). The result is the formation on a sub-second timescale of microparticles composed of the residual solute. Spray-drying has been used as a industrial process in the material,4 food5 and pharmaceutical6, 7 industries for decades. (e.g., see Bergsoe8 for an earlier review). More recently, spray-drying has facilitated the preparation of protein therapeutics as microparticles for inhalation,9 the formulation of advanced carrier-therapeutic microstructures,10-12 and new classes of micromaterials.13-15 The role of kinetic, phase transition, mass transfer, heat transfer, and other physical processes in determining ultimate particle size and composition are well-understood (e.g., see Vehring16 for a recent review), and research in spray-drying is an extremely active area in materials science research. An important finding from this body of research is that in aqueous systems the heat of vaporization reduces the temperature of the particles during the volatilization process. Thus, thermal denaturation of proteins can be minimized for preservation of protein activities.
During World War II, the benefits of whole blood transfusion were appreciated, but logistical difficulties related to collection, transport, outdating and typing mismatch for transfusion reactions limited widespread utilization17. Dried plasma was thus developed as a surrogate for whole blood18. American, British and Canadian military transfusion services extensively utilized dried plasma1 during World War II with a very favorable safety profile. The methods for preparing U.S. Army-Navy dried plasma were originally scaled to commercial volumes by Sharp and Dohme, Inc. (and later by a larger industrial consortium) with lyophilization technologies analogous to today's freeze-drying protocols19. The dried U.S. Army-Navy plasma was anticoagulated with 0.67% (w/v) sodium citrate, and after 1942 was rehydrated with 0.1% (w/v) citric acid. Rehydration with citric acid was found to result in a final product pH of 7.4-7.6 for a more favorable preservation of thrombin generation20.
Dried U.S. Army-Navy plasma was placed in widespread civilian use after 1945, and used in the initial phases of the Korean War. However, despite nascent development of ultraviolet irradiation microbial decontamination methods21, the production of dried plasma was suspended in 1953, the stated reason being hepatitis contamination. However, civilian use of plasma, mostly as fresh frozen plasma, has greatly expanded, with over 13 million units being collected in 200522. In current medical practice plasma is used for a variety of indications, one of the most important being as a component of resuscitation mixtures in trauma with massive blood loss. Plasma contains components, such as the coagulation factors and fibrinogen, which are frequently diminished in hemorrhagic shock-related coagulopathies (e.g., see Hardy et al.23).
Several medical findings point towards the utility of a hyper-concentrated plasma product. The desirability of low volume resuscitation, as facilitated by products such as hyper-concentrated plasma, is becoming increasingly accepted since the initial observations of adverse outcomes related to standard resuscitation.24-26 Incidences of transfusion associated cardiac overload and fluid overload-associated acute respiratory distress syndrome might be avoided with low volume resuscitation.27, 28 Administration of reduced volumes can also be desirable if ongoing hemorrhage is exacerbating dilutional coagulopathies (e.g. see Stern for a review29). The development of advanced resuscitation products, such as hemoglobin-based oxygen carriers (HBOCs),30 facilitate the ability to achieve adequate tissue oxygenation without infusion of large volumes of fluids. However, the introduction of HBOCs is anticipated to create a need for low volume products to supplement hemostatic systems, such as concentrated plasma.
Dried blood products are known in the art, and the predominant technique for achieving the dried product is lyophilization (freeze-drying). For example, U.S. Pat. Nos. 4,287,087 and 4,145,185 to Brinkhous et al. disclose dried blood platelets that have been fixed with a crosslinking reagent such as formaldehyde. U.S. Pat. Nos. 5,656,498, 5,651,966; 5,891,393; 5,902,608; and 5,993,804 disclose additional dried blood products. Such products are useful for therapeutic purposes because they are stable, have long shelf life, and can be used potentially in powder form to arrest bleeding in patients undergoing severe trauma. However, such products must be manufactured under strict sterile conditions in order to avoid contamination.
With current transfusion practices, plasma is frequently provided as a thawed single donor “fresh frozen” product. However, since refrigeration is difficult to provide in forward military applications, underdeveloped countries, and in wilderness medicine situations, this form factor can be logistically problematic. Thus, the elimination of freezing (lyophilization) via a dried plasma product would be a significant advantage. In addition, the dried plasma product is significantly easier to pathogen reduce than is fresh frozen plasma. The present invention is believed to be an answer to that need.